Non-subsidized phones don't necessarily require data (or phone) plans at all.
I have some old android phones I use on wifi only. This new one is on a. Tmo prepaid SIM that ends up costing $15/yr for my very few talk mins and 1yr expiration extension. 2g data is available for $2 if you need it for a day, $3 for 3/4g. I use a freedompop wifi dongle ($99) that comes with 500MB. A month (or 1GB if you jump through a trivial, one-time hoop. Google for info). It's worked fine.